Differential Diagnosis for the 3mm Nodular Finding
- Single most likely diagnosis:
- Surgical clip or artifact: Given that the 3mm nodular finding has been present since 1 month after partial nephrectomy and has "matured" over time, it is likely a benign finding related to the surgical procedure, such as a surgical clip or an artifact from the surgery.
- Other Likely diagnoses:
- Fibrotic change: The nodular finding could represent a fibrotic change in the tissue, which is a common sequela of surgery and would be consistent with the stable appearance over time.
- Benign cyst or simple cyst: Although less likely given the description, a small benign cyst could be considered, especially if the imaging characteristics are not fully indicative of a solid lesion.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
- Metastatic disease: Although the primary tumor was a chromophobe RCC with a favorable prognosis (T1a, 1.3 cm), the possibility of metastatic disease, even if small, cannot be entirely ruled out without thorough investigation. Metastases to unusual locations, including the fat anterior to the psoas muscle, have been reported.
- Local recurrence of RCC: Despite the benign biopsy of the adjacent soft tissue mass, the possibility of a local recurrence of the RCC, potentially in an unusual location, must be considered.
- Rare diagnoses:
- Other benign tumors (e.g., lipoma, neurofibroma): Rarely, small benign tumors could present in this location and might have a similar appearance on imaging.
- Inflammatory or infectious process: An inflammatory or infectious process, potentially related to the surgical site, could theoretically present as a small nodular finding, although this would be less likely given the chronic and stable nature of the finding.